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The dimension of power is energy divided by time. In the International System of Units (SI), the unit of power is the watt (W), which is equal to one joule per second. Other common and traditional measures are horsepower (hp), comparing to the power of a horse; one mechanical horsepower equals about 745.7 watts.
Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time. For example, when a light bulb with a power rating of 100 W is turned on for one hour, the energy used is 100 watt hours (W·h), 0.1 kilowatt hour, or 360 kJ. This same amount of energy would light a 40 ...
The sensitivity of the human eye to various wavelengths. Assuming each wavelength equals 1 watt of radiant energy, only the center wavelength is perceived as 683 candelas (1 watt of luminous energy), equaling 683 lumens. The vertical colored-lines represent the 589 (yellow) sodium line, and popular 532 nm (green), 671 nm (red), 473 nm (blue ...
The energy efficiency ratio (EER) of a particular cooling device is the ratio of output cooling energy (in BTUs) to input electrical energy (in watt-hours) at a given operating point. EER is generally calculated using a 95 °F (35 °C) outside temperature and an inside (actually return-air) temperature of 80 °F (27 °C) and 50% relative humidity.
A kilowatt is a unit of power (rate of flow of energy per unit of time). A kilowatt-hour is a unit of energy. Kilowatt per hour would be a rate of change of power flow with time. Work is the amount of energy transferred to a system; power is the rate of delivery of energy. Energy is measured in joules, or watt-seconds.
In physics and many other areas of science and engineering the intensity or flux of radiant energy is the power transferred per unit area, where the area is measured on the plane perpendicular to the direction of propagation of the energy. [a] In the SI system, it has units watts per square metre (W/m 2), or kg⋅s −3 in base units.
The rate of heat flow is the amount of heat that is transferred per unit of time in some material, usually measured in watts (joules per second). Heat is the flow of thermal energy driven by thermal non-equilibrium, so the term 'heat flow' is a redundancy (i.e. a pleonasm). Heat must not be confused with stored thermal energy, and moving a hot ...
HSPF is defined as the ratio of heat output (measured in BTUs) over the heating season to electricity used (measured in watt-hours). [1] [2] It therefore has units of BTU/watt-hr. The higher the HSPF rating of a unit, the more energy efficient it is. An electrical resistance heater, which is not considered efficient, has an HSPF of 3.41. [3]